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SPECIAL STEELS

SPECIAL STEELS

Special or higli-spe-etl steels, now largely used, are characterised by the
presence of some suitable, clement, such as chromium, tungsten, nickel,
etc., which confers quite special properties. The chemical analysis of
special steels includes, therefore, besides the ordinary determinations, those
of the specific, elements present. Tests will first be given for the identifi-
cation of these elements.

Qualitative Tests

1.  Detection of Chromium.    A little of the finely powdered sample
is heated on the cover of a, platinum crucible or in a. porcelain dish and the
residue fused with sodium carbonate and nitre.     In presence of chromium,
a more or less intensely yellow mass is obtained,    1 f a solution (which should
be acid) of this in dilute acetic acid is treated with silver nitrate, a, brick-
red precipitate is obtained.

2.  Detection of Nickel.A little of the sample is dissolved in hydro-
chloric acid, the iron oxidised with nitric acid and a little tartario acid (2
grams per 0-5 gram of the steel) dissolved in a. little water added.   The
liquid is then made alkaline with ammonia and heated with a. little 1%
solution of dimcthylgiyo.vime iu alcohol :  a red precipitate indicates nickel.

3.  Detection  of  Mun^anene.    (</) A   little  of   the   finely   powdered
sample is heated on a platinum crucible cover or in a porcelain dish and
the residue fused with sodium carbonate and  nitre,    (/) The sample is
treated with nitric acid (I) r.;) and the solution heated with a little lead
peroxide free from manganese.    When the peroxide settles, the liquid will
exhibit, a, violet-red colour if manganese is present.    This reaction is very
sensitive and with ferro'manganese, a very small quantity must be taken,

4.  Detection of Tungsten.    A little of the finely powdered snmple
is fused with sodium carbonate and nitre, the ma--w being, taken up in hot
water and the solution tittered, acidified strongly with hydrochloric, acid
and heated,    In presence of tungsten, a while precipitate is obtained, turning
yellow on heating1;   this consists of anhydrous tungstic arid and is soluble

in sodium carbonate.

5.  Detection of Vanadium.    A little of the sample is dissolved in
nitric acid (D  - 1-iH) and a. small quantity of hydrogen peroxide allowed
to How down the side of the tube.    In presence of vanadium, a reddish-
brown coloration is formed at the /one of contact of the two liquids.

6.  Detection of Molybdenum.    A little of the finely powdered sample
is heated and the. residue fused with sodium carbonate and nitre, the mass
being treated with hot water and filtered.    The filtrate is strongly acidified
with sulphuric acid, evaporated and healed until white fumes appear,   A
little cone, sulphuric acid is stirred into the cold liquid and, without diluting,
alcohol is added.    In presence of molybdenum an intense blue coloration
is obtained.   This coloration disappears on dilution with water, and if the
liquid is then subjected in the hot, to the action of hydrogen sulphide, a
brown precipitate of molybdenum sulphide is obtained.of arsenic,iodine number of fatty